Little is known about the occurrence of or the temporal relationships between human sperm capacitation, the acrosome reaction and changes in flagellar motility. Since it is important to an understanding of human male fertility and infertility to define the characteristics of these fertility related events and their regulation, three specific aims are proposed: Define the characteristics of a normal fertile human sperm. Sperm from fertile donors under in vivo conditions known to support homologous fertilization will be examined for capacitation, the extent and inducibility of the acrosome reaction as well as for changes in specific parameters of flagellar motility; determine if the characteristics defined for normal sperm are altered in sperm from patients of reduced fertility or in sperm treated in vitro to enrich for the proportion of fertile sperm; and examine the molecular basis for these alterations in sperm function by dissecting specific pathways suggested to be involved in the regulation of capacitation, the acrosome reaction and associated changes in flagellar motility, with particular attention to cAMP and calcium. Human sperm capacitation will be measured with the zona-free hamster egg bioassay and acrosomal status will be evaluated before and after exposure to calcium ionophore by indirect immunofluorescence using a specific monoclonal antisperm antibody. Specific aspects of flagellar motility will be measured by computer-assisted video image analysis. Examination of the regulatory pathways involved in sperm function will center on the role of calcium, calmodulin, calmodulin binding proteins, cAMP, cAMP-dependent protein kinase and proteins phosphorylated by the latter. Results from these studies should provide the basis from which the development of new diagnostic procedures and treatment modalities can be approached for the sub- or infertile human male.